EFFECTS OF TIME AND NEST-SITE CHARACTERISTICS ON CONCEALMENT OF SONGBIRD NESTS

We studied the effect of time and nest-site characteristics on nest co ncealment measurements and analyzed differences in concealment between parasitized, nonparasitized, depredated, and fledged nests. Mean conc ealment at nests of three old-field bird species was best explained by bird species, nest plant and height of the nest. Nests lost concealme nt over time, particularly those placed high in shrubs or roses (Rosa spp.). Mean and minimum concealment did not explain occurrence of pred ation or brood parasitism for any of the three bird species, and conce alment at parasitized versus unparasitized nests and depredated versus fledged nests did not change differently over time. A literature revi ew showed that most studies of real passerine nests using visual nest concealment have taken measurements after nest termination, and few st udies indicated that concealment was important in explaining nest pred ation or brood parasitism. Late concealment measurements may be an add itional source of error in nesting studies, especially if predation or parasitism is more likely to occur at nests sharing similar vegetatio n characteristics.